These are instructions on how to untether your jailbreak of iOS 4.2.1 using the latest version of Redsn0w 0.9.7b4 on Mac OS X. Currently this beta is limited to iPhone4, iPad, and iPod touch 4G. Bluetooth functionality is disabled for the time being until some issues are resolved.
You will need: Have access to the iOS 4.2b3 ipsw and your iOS 4.2b3 SHSH blobs saved. You also already need to be jailbroken on iOS 4.2.1 (Full Guide). MAKE SURE YOU BACKUP BEFORE ATTEMPTING THIS AS IT IS A BETA!
Download Redsn0w 0.9.7b4 for Mac OS X
Download iOS 4.2.1 for iPhone, iPad and iPod touch
Download iTunes 10.1.1 for Windows / Mac OS X
Download iOS 4.2 Beta 3 for iPhone, iPad and iPod touch
Create a folder called Pwnage on your desktop and in it place: iOS 4.2.1 and iOS 4.2b3 *Only iPhone developers have legit access to this firmware
Double click the RedSn0w archive to extract it. Then launch RedSn0w from the extracted folder.
Click the Browse button
Select the iOS 4.2.1 ipsw from the Pwnage folder on your Desktop and click Open.
Click the Next button to continue.
RedSn0w will now prepare the jailbreak data.
You will now be presented with a list of checkboxes.
Select Jailbreak Monte (untether) from the list of checkboxes. You will be asked to select the iOS 4.2b3 ipsw from the Pwnage folder on your desktop then click Open. Click Next to continue.
Please plug your iPhone into the computer and make sure its OFF then click the Next button
RedSn0w will now guide you through the steps to get into DFU mode. You can find more help with DFU mode here
Hold down both the Home button and the Power button for 10 seconds.
Release the Power button and continue holding the Home button until RedSn0w detects the device.
RedSn0w will prepare Jailbreak Monte files, exploit with Limera1n, Upload RAM Disk and Kernel, and Send Jailbreak Monte files.
RedSn0w will inform you when it has completed successfully.
This guide is for educational purpose only, we are not responsible if you brick your device!